The invention relates to a high-pressure discharge lamp provided with a discharge vessel which is enclosed with intervening space by an outer bulb and is provided with a starter circuit comprising at least a bimetal switch with a bimetal element, which element is fastened with a fastening point to a conductor and rests against a break contact point of a break contact of the bimetal switch in the cold state.
The invention also relates to a bimetal switch suitable for use in a starter circuit of a discharge lamp and to a starter unit provided with such a bimetal switch.
A lamp of the kind mentioned in the opening paragraph is known from EP-A-0 345 873, which corresponds to U.S. Pat. No. 4,981,330.
In the known lamp, the fastening point of the bimetal element is fastened to an electrical supply conductor extending to a lamp electrode.
The contact point of the break contact is formed by a conductor which is wound around the discharge vessel so as to form a wire winding, which conductor is connected to a further electrical supply conductor via a glowswitch starter.
Although the construction as a wire winding around the discharge vessel provides a good definition of the contact point of the break contact, it is found in practice that fastening of the bimetal element to the supply conductor often leads to problems. For example a small tangential displacement of the fastening point of the bimetal element on the supply conductor will already have a major influence on the position of the bimetal element relative to the contact point of the break contact. This may easily give rise to an incorrect functioning, or a failure to function altogether, of the bimetal switch. An incorrect adjustment of the bimetal element thus created can only be corrected in a separate aftertreatment during the lamp production process by means of a readjustment of the mechanical pretensioning of the bimetal element. The said displacement leads to production rejects in those cases in which no repair is found to be possible.
The invention has for its object to provide a means by which the above disadvantages can be counteracted.